Case of the Month

February 1, 2009 Diagnostic Imaging. Vol. 31 No. 2 Case of the Month FigureCLINICAL HISTORY A 44-year-old Asian man with a past medical history of left carotid artery stenosis presented to the emergency room with sudden onset of severe headache. An initial noncontrast head CT scan revealed acute hemorrhage within the left lentiform nucleus. CT angiography was subsequently performed for further evaluation. FINDINGS Axial CTA image at the level of the cavernous sinuses (Figure 1) demonstrates circumferential narrowing of the left internal carotid artery. Axial and coronal CTA reconstructions (Figures 2 and 3) demonstrate enlarged left lenticulostriate collateral arteries with a characteristic “puff of smoke” appearance. DIAGNOSIS Moyamoya disease. DIFERENTIAL DIAGNOSIS The top differential diagnoses include carotid thromboembolic disease or various types of vasculitis. DISCUSSION Moyamoya, which in Japanese means “puff of smoke,” was first described in Asian children presenting with symptoms of cerebral ischemia. While it is most prevalent in Japan, it is not limited to this particular population. The female to male ratio is approximately 1.8:1, with symptoms occurring in either the first or the third to fourth decades of life. Moyamoya may be familial or secondary to a variety of disorders that may cause progressive obliteration of the distal internal carotid artery. Disease entities most often linked to Moyamoya include severe atherosclerosis, vasculitis, neurofibromatosis, tuberous sclerosis, and sickle cell disease. Moyamoya is characterized by progressive stenosis of the supraclinoid internal carotid artery and proximal branches of the circle of Willis, ultimately leading to extensive collateralization via leptomeningeal, thalamoperforate, lenticulostriate, and transdural vessels that supply the ischemic brain. Collateral vessels tend to become ectatic and may even develop small aneurysms. Changes in blood pressure may result in aneurysm rupture and hemorrhage. In adults, Moyamoya disease most commonly presents as intraparenchymal or subarachnoid hemorrhage, while in the pediatric population, it typically manifests as symptoms of cerebral ischemia. The radiological findings of Moyamoya are most frequently characterized on conventional or angiographic CT studies. As intravenous contrast passes through the stenotic internal carotid artery into the dilated netlike configuration of collateral vessels, it produces the characteristic “puff of smoke” sign. While conventional angiography is considered the definitive means of diagnosis, CTA as well as MRA have gained favor, because they are less invasive and pose a lower inherent risk to the patient. MRA is recommended as a means of periodic follow-up, particularly in the pediatric population, where exposure to ionizing radiation is of greatest concern. Submitted by Alan V. Krauthamer, M.D., and Vadim Spektor, M.D., both at St. Vincent's Medical Center in New York City. BIBLIOGRAPHY Ortiz-Neira CL. The puff of smoke sign. Radiology 2008; 247:910-911. Osborn A, Blaser S, Salzman K, eds. Diagnostic imaging: brain. Salt Lake City: Amirsys 2004;I4:42-45. Takahashi M, Miyauchi T, Kowada M. Computed tomography of Moyamoya disease: demonstration of occluded arteries and collateral vessels as important diagnostic signs. Radiology 1980;134:671. Yamada I, Suzuki S, Matsushima Y. Moyamoya disease: Comparison of assessment with MR angiography and MR imaging versus conventional angiography. Radiology 1995;196:211.

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